Lookdown \Look"down`\, n. (Zo["o]l.) See Moonfish
   (b) .

Source: Webster's Revised Unabridged Dictionary (1913)
 

Moonfish \Moon"fish`\, n. (Zo["o]l.)
   (a) An American marine fish (Vomer setipennis); -- called also bluntnosed shiner, horsefish, and sunfish.
   (b) A broad, thin, silvery marine fish (Selene vomer); -- called also lookdown, and silver moonfish.
   (c) The mola. See Sunfish, 1.

Source: Webster's Revised Unabridged Dictionary (1913)